<counteropinion>

Unless performance is a concern, go with what's most readable.

For a lone string test, use lc() and eq. But if you've already used a couple of regex's to test $foo, it may be more readable to throw in another one, rather than switching gears and using lc() and string compare.

Consider adding a test below this fragment:

  next if $foo =~ /^#/;
  if ( $foo =~ /^(?:this|that|or|something|else)$/ { ... }
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Now which reads better   if ( $foo =~ /^$bar$/i ) { ... } or   if ( lc($foo) eq lc($bar) ) { ... } I'll argue that it's at best a toss-up. As a reader of fragments like this, I see the pattern of a variable being tested against a sequence of regex's, and my brian goes into regex scanning mode. Mixing in a string comparision might be technically correct, but it breaks up the reading flow, at least in examples like this.

</counteropinion>