sub files_differ {
  system "cmp file1 file2";
 return $? >> 8;
}
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Windows has no "cmp" command. $? is set to 0x0100, files_differ always returns 1, even with missing files, even with identical files. Instant fail.

H:\>perl -e "system 'cmp file1 file2';print $?,' ',$? >> 8"
'cmp' is not recognized as an internal or external command,
operable program or batch file.
256 1
H:\>
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And by the way: Omitting quotes around the file name begs for trouble as soon as you replace the constants with variables. Using the multiple argument form of system would prevent that problem.

Alexander

I have a cmp command on my windows system. There is also the comp command which has been available on all versions of windows:

C:\test>cmp
cmp: missing operand
cmp: Try `cmp --help' for more information.

C:\test>comp /?
Compares the contents of two files or sets of files.

COMP [data1] [data2] [/D] [/A] [/L] [/N=number] [/C] [/OFF[LINE]]

  data1      Specifies location and name(s) of first file(s) to compar
+e.
  data2      Specifies location and name(s) of second files to compare
+.
  /D         Displays differences in decimal format.
  /A         Displays differences in ASCII characters.
  /L         Displays line numbers for differences.
  /N=number  Compares only the first specified number of lines in each
+ file.
  /C         Disregards case of ASCII letters when comparing files.
  /OFF[LINE] Do not skip files with offline attribute set.

To compare sets of files, use wildcards in data1 and data2 parameters.
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---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

have a cmp command on my windows system.

Because you installed it? At least the DOS-based Windows versions (1.x, 2.x, 3.x, 95, 98, ME), Windows 2000 and Windows XP lack a cmp command after a fresh installation.

Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)

Quite agree on the list form invocation; that's a much better choice. I always forget it, for some reason.

Re no cmp on Windows: that just means this isn't the simplest possible thing for Windows. I'm sure there is an equivalent.