Re: using shift and $

You never assigned to $_. The equivalent of

sub scribble {
   while ( $a = shift ){
      $a; # has arg
   }
}
[download]

that assigns to $_ is

sub scribble {
   while ( $_ = shift ){
      $_; # has arg
   }
}
[download]

In both cases, you are using global variables. $_ is particularly dangerous to clobber. Fix:

sub scribble {
   local $_;
   while ( $_ = shift ){
      $_; # has arg
   }
}
[download]

Comment on Re: using shift and $_ in loop Select or Download Code

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Re^2: using shift and $_ in loop by leocharre (Priest) on Oct 21, 2009 at 15:59 UTC
Thank you, this is really useful. So, you suggest localizing $_ as a precaution?	[reply]
Re^3: using shift and $_ in loop by ikegami (Patriarch) on Oct 21, 2009 at 16:37 UTC
Yeah, don't clobber your caller's variables.	[reply]
Re^4: using shift and $_ in loop by leocharre (Priest) on Oct 21, 2009 at 20:26 UTC
Don't clobber your caller's variables.. so.. in .. `sub a { @_; $_; }` [download] $_ is .. what of the caller? And am I to understand that in sub a, messing with @_, regardless if the caller passed any references as arguments, is potentially messing with the caller's arguments? (thank you for your patience here)	[reply] [d/l]
Re^5: using shift and $_ in loop by ikegami (Patriarch) on Oct 21, 2009 at 20:34 UTC