checking image file <[^>]+>
...
checking image file <[^>]+\.f>

##</code><code>##

my $file = "";

{
  local $/ = undef;
  $file = <INFILE>;
}

my %failures = ();

while(my ($image, $msgs) = $file =~
  /checking image file <([^>]+)>
   (.+?media does not exist.+?)
   checking image file <$1\.f>/gsx)
{
  $failures{$image} = 1;
}