Re: Check for hash ref emptiness

[NetWallah]

The regex check will do nothing if the value is empty, so your 'if' check is unnecessary.

Instead of checking for 'empty', you should be checking 'defined-ness' - which , for a hash uses 'exists':

if ( exists $data->{classes}  and defined $data->{classes} ){
  $data->{classes} =~ s/XY//g;
}

UPDATE: Added 'defined' check, per comment by AnomalousMonk(++), below.

[AnomalousMonk]

... you should be checking 'defined-ness' - which , for a hash uses 'exists' ...

A hash key may exist and its value be undefined. If it is undefined, a warning will be produced by an operation like matching if warnings are enabled — as we hope they (almost) always are! See exists.