my $x = "(quantifier)";
my %x = ( "1" => "(hash_value)" );
my $z = 'quantifier hash_value';

print "_$1_\n" if $z =~ /$x{1}/;         # {1} is quantifier
print "_$1_\n" if $z =~ /@{[$x{1}]}[0]/; # {1} is hash key 

__END__

_quantifier_
_hash_value_