Instead of system "perl converter.pl $_" you could use do. If you could rewrite converter.pl to work on $_ you could replace your loop with do "converter.pl" for @files. Or even better if converter.pl can work on all arguments:

{
    local @ARGV = @files;
    do "converter.pl";
}
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And if you don't want to rewrite converter.pl :

foreach (@files)
{
   local @ARGV = $_;
   do "converter.pl";
}
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