scalar(@$colref) is the number of items found in the column, it would never contain a '#' symbol.

$colref->[0] is the first item on the line read in, it could contain a # symbol.

if ($colref->[0] =~ /^#/) { next; }
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Notice i said next rather than last. next will go on to the next row, last will end the do loop and stop reading any more lines.

the next condition is a touch more tricky.

 
my $anynonblank=0; 
for my $item (@$colref){ 
  unless  ($item =~ /^\s+$/) { $anynonblank=1; last; } 
} 
unless ($anynonblank) { next; }
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edit: opps , fixed as per Re^6: Read CSV with column mapping below