#! /bin/bash

# helper script simulator

VAR="  fu   bar\n  foo \n\n   bar \n\n\n  baz "


echo -e "$VAR" | perl -nE '
# this code is used inside a loop because of -n option
    s/^\s+//;           # remove leading whitespaces from lines
    s/\s+$/ /;          # replace trailing whitespaces (including newlines) with a single whitespace
    $output .= $_;      # append to a variable for later output

# at the end, do this
END {
  $output =~ s/\s+$//;  # remove trailing whitespace
  say qq~>$output<~;    # testing output
  #say $output;         # production output
}
' #END_OF_PERL