You say tomato, I say $tomato

When I first started programming thirty or so years ago, my choice of language was simple: machine code or bust. I didn't like machine code much, so I never wrote very much. A pattern, however, was established which would be maintained for a long time. A limited set of computer languages would be available at any one time, and I would pick the one that I liked the best and work solely in that. Machine code gave way to assembler (never mastered) to BASIC to APL to Pascal. Transitions were short and sweet; once a better language was available to me, I switched completely. A few languages (Logo, Forth, Modula 2) were contemplated, but never had the necessary immediate availability to be adopted.
A summer internship tweaked the formula slightly -- at work I would use RS/1, because that's what the system was, but at home I stuck to Pascal. For four years of college this was the pattern.

Grad school was supposed to mean one more shift: to C++. However, soon I discovered the universe of useful UNIX utility languages, and sed and awk and shell scripts started popping up. Eventually I discovered make, which is a very different language. A proprietary GUI language based on C++ came in handy. Prolog didn't quite get a proper trial, but at least I read the book. Finally, I found Perl and tried to focus on that, but the mold had been broken -- and for good measure I wrote one of the worlds first interactive genome viewers in Java. My thesis work consisted of an awful mess of all of these.

Come Millennium, I swore I would write nothing but Perl. But soon, that had to be modified as I needed to read and write relational databases, which requires SQL. Ultimately, I wanted to do statistics -- and these days that means R.

There are a number of computer language taxonomies which can be employed. For example, with the exceptions of make, SQL (as I used it) and Prolog all of these languages are procedural -- you write a series of steps and they are executed. The other three fit more of a pattern of the programmer specifying assertions, conditions or constraints and the language interpreter or compiler executes commands or returns data according to those specifications.

Within the procedural languages, there is a lot of variation. Some of this represents shared history. For example, C++ is largely an extension of C, so it shares many syntactic features. Perl also borrowed heavily from C, so much is similar. R is also loosely in the C syntax family. All of these languages tend to be terse and heavily use non-alphabetic characters. On the other hand, SQL is intrinsically loquacious.

The fun part is when you are trying to use multiple languages simultaneously, as you must keep straight the differences & properly shift gears. Currently, I'm working semi-daily in Perl, SQL and R, and there is plenty to catch me up if I'm napping. For example, many Perl and R statements can interchange single and double quotes freely -- as long as you do so symmetrically; SQL needs single quotes around strings.
Perl & R use the C-style != for inequality; SQL is the older style <> and in paralled Perl & R use == for equality whereas SQL uses a single = -- and since a single = in Perl is assignment, forgetting this rule can lead to interesting errors! R is a little easier to keep straight, as assignment is <- . R and Perl also diverge on $ -- for Perl it precedes every single value (scalar) variable, whereas in R it specifies a column of a table. I haven't done C++ or Java for over ten years, but my mind still wants to parse an R variable foo.bar as bar is a member of class instance foo (perhaps because that's the SQL idiom as well), but in R the period is just another legal character for composing a name -- and in Perl it's yet another syntax ( ->{'key'} ) to access the members of a class.

While I know all the rules, inevitably there is a mistake a day (or worse an hour!) where my R variables start growing $ and I try to select something out of my SQL using != . Eventually my mind melts down and all I can write is:

select tzu->{'name'},shih$color from $shih,$tzu where shih.dog==tzu.dog

which doesn't work in any language!