Assuming you mean get the X numbered character from the string, you could do...

sub chr_at {
  my ($data, $skip) = @_;
  --$skip;

  $data =~ /^.{$skip}(.)/;
  $1; 
}

for (1..4) {
  print chr_at("abcd", $_) . "\n";
}
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...but I wouldn't be supprised if the substr() version is faster.