Prefer fixed-string eq comparisons to fixed-pattern regex matches .
If you're trying to compare a string against a fixed number of fixed keywords, the temptation is to put them all inside a single regex, as anchored alternatives:
# Quit command has several variants...
last COMMAND if $cmd =~ m{\A (?: q | quit | bye ) \z}xms;The usual rationale for this is that a single, highly optimized regex match must
surely be quicker than three separate eq tests:
# Quit command has several variants...last COMMAND if $cmd eq 'q' || $cmd eq 'quit' || $cmd eq 'bye';
Unfortunately, that's not the case. Regex-matching against a series of fixed alternations is at least 20% slower than individually eq-matching the same stringsnot to mention the fact that the eq-based version is significantly more readable.
Likewise, if you're doing a pattern match merely to get case insensitivity:
# Quit command is case-insensitive...
last COMMAND if $cmd =~ m{\A quit \z}ixms;then it's more efficient, and arguably more readable, to write:
# Quit command is case-insensitive...last COMMAND if lc($cmd) eq 'quit';
Sometimes, if there are a large number of possibilities to test:
Readonly my @EXIT_WORDS => qw( q quit bye exit stop done last finish aurevoir );
or the number of possibilities is indeterminate at compile time:
Readonly my @EXIT_WORDS => slurp $EXIT_WORDS_FILE, {chomp=>1};
then a regex might seem like a better alternative, because it can easily be built on the fly:
Readonly my $EXIT_WORDS => join '|', @EXIT_WORDS;
# Quit command has several variants...
last COMMAND if $cmd =~ m{\A (?: $EXIT_WORDS ) \z}xms;But, even in these cases, eq offers a cleaner (though now slower) solution:
use List::MoreUtils qw( any );
# Quit command has several variants...last COMMAND if any { $cmd eq $_ } @EXIT_WORDS;
Of course, in this particular case, an even better solution would be to use table look-up instead:
Readonly my %IS_EXIT_WORD => map { ($_ => 1) } qw( q quit bye exit stop done last finish aurevoir );
# and later... # Quit command has several variants...last COMMAND if $IS_EXIT_WORD{$cmd};