#!/usr/bin/perl -wT
use strict;

my $txt   = '$a @b $c %d';
my $out1  = quotemeta($txt);
(my $out2 = $txt) =~ s/([\$\@])/\\$1/g;

print "txt  = $txt\n";
print "out1 = $out1\n";
print "out2 = $out2\n";

=OUTPUT
txt  = $a @b $c %d
out1 = \$a\ \@b\ \$c\ \%d
out2 = \$a \@b \$c %d