#!/usr/bin/env perl
#Adds trivial "alt=pix" tag to <img src=...>, in order to
#satisfy "Bobby compliance". http://www.cast.org/bobby/
#example usage: bobby.pl *.html 
for $file (@ARGV){  # @ARGV contains  *.html glob
  print "$file\n"; #print name of file being modified
  open INFILE,"<$file"; 
  @all=<INFILE>;  #put the lines of the file into an array
  close INFILE;
  open OUTFILE,">$file"; #reopen file for writing
  for $line (@all){
    #Note the three groupings in ( ) in the first match search.
    #Not only match "<img src=...", but check that "<img src=..."
    #does not already have "alt" tag.  $1, $2 and $3 are the matches in
    #the ()()(). =~m means look for match in string on left. !~m means look for NOT match.
    if ( ($line=~m/(<\s*img\s+src=)(.*?)(>)/) && ($2!~m/alt=/) ){
      print $line; #print line before modification
      #~s means substitute 2nd / / for first / /.  Note use of $1 and $2,
      #which back references to the ( ) and ( ) in the first / /.
      $line=~s/(<\s*img\s+src=.*?)(>)/$1 alt="pix"$2/;
      print $line,"\n"; #print line after modification, and skip a line.
    }
  	print OUTFILE $line; #print line, modified or not, out to file
  }
  close OUTFILE;
}