join "|", map { "\\b$_\\b" } reverse sort keys %cats;
I'd suggest putting a quotemeta in there, just to play it safe. Although I agree that using a proper parser is better! skooma: See also Building Regex Alternations Dynamically.
use warnings;
use strict;
use Test::More;
my %cats = (blackcat=>5, whitecat=>10,orangecat=>20);
my ($regex) = map { qr/\b($_)\b/ } join '|', map {quotemeta}
sort { length $b <=> length $a or $a cmp $b } keys %cats;
diag explain $regex;
sub do_replace {
my $input = shift;
$input =~ s/$regex/$cats{$1}/g;
return $input;
}
is do_replace("log10(blackcat)"), "log10(5)";
is do_replace("log10(blackcat)*whitecat*(log10(orangecat))"),
"log10(5)*10*(log10(20))";
done_testing;
__END__
# qr/\b(orangecat|blackcat|whitecat)\b/
ok 1
ok 2
1..2