if( length($string) > 0 ) {
  # do something
}

##</code><code>##

if( length($string) > 50 ) {
  # cut the string and either add ... to show it was truncated.
  $string = substr( $string, 0, 47 ) . '...';
  # alternatively, or not
  $string = substr( $string, 0, 50 );
}

##</code><code>##

my $MAXLEN = 50;
if( length($string) > $MAXLEN ) {
  # cut the string and either add ... to show it was truncated.
  $string = substr( $string, 0, $MAXLEN-3 ) . '...';
  # alternatively, or not
  $string = substr( $string, 0, $MAXLEN );
}