From ryan.royal@airbus.com

A bare word file handle causes the readline(FH) function to emit a warning​: Name "main​::FH" used only once​: possible typo at readline_test.pl line 4.

-The equivalent diamond operator <FH> used on the same bare word handle does not evoke the warning.

-Using a lexically scoped file handle with readline( $fh ) also does not evoke the warning.

See attached, thanks

========================== version ===========================
Strawberry Perl

C​:\Home\RRoyal02\MyPrograms\perl\bin> perl5.24.0 -v

This is perl 5, version 24, subversion 0 (v5.24.0) built for MSWin32-x64-multi-thread

Copyright 1987-2016, Larry Wall

=========================== OS ============================
Windows 7 Enterprise
Intel Xeon CPU
32 GB Ram

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From ryan.royal@airbus.com

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From @iabyn

On Mon, Jan 30, 2017 at 08​:44​:36AM -0800, ROYAL@​rt.perl.org wrote​:

# New Ticket Created by ROYAL, Ryan
# Please include the string​: [perl #130673]
# in the subject line of all future correspondence about this issue.
# <URL​: https://rt-archive.perl.org/perl5/Ticket/Display.html?id=130673 >

A bare word file handle causes the readline(FH) function to emit a warning​: Name "main​::FH" used only once​: possible typo at readline_test.pl line 4.

-The equivalent diamond operator <FH> used on the same bare word handle does not evoke the warning.

readline takes a typeglob as an argument, while the <> operator takes the
*name* of a typeglob, So, as the docs for readline say,

  $line = <STDIN>;
  $line = readline(*STDIN); # same thing

Note that one has a '*', the other doesn't. However, readline will accept
a bareword string, and at runtime use it as the name of a typeglob to look
up.

So at *compile* time (at which time 'only used once' warnings are checked
for and issued),

  <FH>

is compiled as

  readline *FH

and a typeglob check is done; while

  readline FH

is compiled as

  readline 'FH'

and no typeglob is involved or checked for,

Note that 'readline *FH' *will* give a warning.

It might be possible to change it so that in 'readline FH', the "FH"
string is converted to a typeglob at compile time, but personally I'm in
favour of leaving anything filehanldle/typeglob related well alone. It has
a ton of edge-case weird semantics inherited from perl4 days.

-Using a lexically scoped file handle with readline( $fh ) also does not evoke the warning.

Lexicals don't give 'only used once' warnings in any situation, not just
readline.

--
I before E. Except when it isn't.

The RT System itself - Status changed from 'new' to 'open'

@iabyn - Status changed from 'open' to 'rejected'