use warnings;
use strict;

my @repls = (
    [ qr/pat(\d+)/, 'qq{repl$1}' ],
);

my $txt = <<'EOF';
This is some example (pat42) text
EOF

foreach my $r (@repls) {
    $txt =~ s/$r->[0]/$r->[1]/eeg;
}

print $txt;
__END__
This is some example (repl42) text