You might want to explore using a hash with the regular expression as the key and the replacement text as the value. You can use compiled regular expressions as hash keys. You might need to consider using \Q and \E or quotemeta when compiling the regular expressions. In the script below I read the patterns and corresponding replacements from the DATA file at the end of the script and the patterns contain no spaces so a simple split on white space is sufficient. Your patterns may be more complex.

use strict;
use warnings;

my %substitutions = ();
while ( <DATA> )
{
    chomp;
    my ($pattern, $replace) = split;
    my $rxPattern = qr{(?si)$pattern};
    $substitutions{$rxPattern} = $replace;
}

my $str = q{a capital M and Fish};
print qq{$str\n};

$str =~ s{$_}{$substitutions{$_}}
   for keys %substitutions;

print qq{$str\n};

__END__
\s*M\s* MALE
\s*F\s* FEMALE
[download]

The output produced is

a capital M and Fish
a capitalMALEandFEMALEish
[download]

I hope this is of use.

Cheers,

JohnGG