Saving the whole array and then popping off the last element uses up lines and adds variables. I'd rather wrap the split in parentheses and reference the last element.

my $suffix = ( split /\./, $filename )[-1];
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The only danger is that if the only reason you're getting the suffix is to print it, you need more parentheses to prevent print from thinking a subset of the expression is its argument list:

print ( split /\./, $filename )[-1];   # wrong
print (( split /\./, $filename )[-1]); # unpleasant
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