my $flip = 'vh';
if( $flip =~/v|y/i ){ print "i only -> flip v|y\n"; }
if( $flip =~/h|x/i ){ print "i only -> flip h|x\n"; }

if( $flip =~/v|y/ig ){ print "ig -> flip v|y\n"; }
if( $flip =~/h|x/ig ){ print "ig -> flip h|x\n"; }

if( $flip =~/v|y/g ){ print "g only -> flip v|y\n"; }
if( $flip =~/h|x/g ){ print "g only -> flip h|x\n"; }

#change $flip
print "----------------------\n\$flip is now $flip\n----------------------\n";
$flip = 'hv';
if( $flip =~/v|y/i ){ print "i only -> flip v|y\n"; }
if( $flip =~/h|x/i ){ print "i only -> flip h|x\n"; }

if( $flip =~/v|y/ig ){ print "ig -> flip v|y\n"; }
if( $flip =~/h|x/ig ){ print "ig -> flip h|x\n"; }

if( $flip =~/v|y/g ){ print "g only -> flip v|y\n"; }
if( $flip =~/h|x/g ){ print "g only -> flip h|x\n"; }

##</code><code>##

i only -> flip v|y  (expected this)
i only -> flip h|x  (expected this)
ig -> flip v|y      (expected this)
ig -> flip h|x      (expected this)
g only -> flip h|x  (expected this)
                    <--- didn't match v 
----------------------
$flip is now vh
----------------------
i only -> flip v|y   (expected this)
i only -> flip h|x   (expected this)
ig -> flip v|y       (expected this)
                    <--- didn't match h
g only -> flip v|y   (expected this)
                    <---- didn't match h