Another surprising aspect is context. The fact that functions or even variables behave differently depending on whether they're referenced in list or scalar (or void) context has been an important detail for Perl trainees.
I usually insist on "higher-level" built in functions (map, grep, splice, split). Because of TMTOWTDI, many programmers only remember the more familiar aspects of Perl (like the C-style loops, substr and index) and use exclusively those.
After they are familiar with the language, Intermediate Perl and Advanced Perl Programming can give them further insights into the world of Perl
