I describe each sub, and then put a few comments here and there. But when I need to use this sub somewhere in a program, I usually just include a condensed version.

################################################# Trim
#
# This function removes whitespace, newline
# characters and other special characters
# before and after STRING. Returns a new string.
#
#   Usage: STRING = Trim(STRING)
#

sub Trim
{
  my $T = $_[0];
  defined $T or return '';
  my $N = length($T);
  my $X = 0;  # ptr to first non-whitespace
  my $Y = 0;  # ptr to last non-whitespace
  while ($N--)
  {
    if (vec($T, $N, 8) > 32)
    {
      $X = $N;
      $Y or $Y = $N + 1;
    }
  }
  return substr($T, $X, $Y - $X);
}
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Condensed version:

sub Trim { my $T = $_[0]; defined $T or return ''; my $N = length($T); my $X = 0; my $Y = 0; while ($N--) { if (vec($T, $N, 8) > 32) { $X = $N; $Y or $Y = $N + 1; } } return substr($T, $X, $Y - $X); }