Use eval to cache the substitution in an anonymous sub:

use strict;
use warnings;

# Cached Regex's: LHS, RHS, Modifiers
my @re_rules = ( 
    ['(?:this|or|that)', 'bob', 'gsi'],
    ['(?:One|Two|Three)', 'Four', 'gs'],
);

my @re_subs = map {
    my $sub = eval "sub { s/$_->[0]/$_->[1]/$_->[2] for (\@_)}";
    die $@ if $@;
    $sub;
} @re_rules;

my @strings = ('this one or that other', 'One two Three');

for my $string (@strings) {
    $_->($string) for (@re_subs);
    print "$string\n";
}
[download]

Or just declare the anonymous subs yourself if you don't need the special markup:

use strict;
use warnings;

my @re_subs = (
    sub { s/(?:this|or|that)/bob/gsi for (@_) },
    sub { s/(?:One|Two|Three)/Four/gs for (@_) },
);

my @strings = ('this one or that other', 'One two Three');

for my $string (@strings) {
    $_->($string) for (@re_subs);
    print "$string\n";
}
[download]

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