sub contents {
  open (FH, "< $FileInfoName") or die "Can't open $FileInfoName for re
+ad: $!";
 my @lines = <FH>;

# return @lines;  # 1st problem: in scalar context, number of lines is
+ returned
#                   2nd problem: next line is never reached

 close FH or die "Cannot close $FileInfoName: $!";

 return join("", @lines); # fix: one big string with all lines concate
+nated
                          # See also File::Slurp
}
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See module File::Basename to extract the directory name (dirname()) from the path, you already have. See module Cwd to get current working directory - if required.

Update: oops - you wanted contents() to return an array (Perl: list) -- then you can keep the return @lines; (in last line) and change the callers context as toolic suggested.

Maybe two other suggestions?

Avoid globals like $FileInfoName, use a parameter to contents() instead.

A more contemporary way is the three-arg-open plus avoiding globs like FH:
e.g: open(my $file, '<', $FileInfoName) or die "..."; my @lines = <$file>; ...
(and maybe chose a better name than $file (as I did here ;-) - something that is meaningful in the given context.