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Perl Binding,
By A.P. Lawrence
Expert Author
Article Date: 2005-10-25
Perl has "||" and "or". While "or" can't be used in bit operations, either one can be used in logical flow control - but there is an important difference between them.
For example, this code doesn't work properly:
#!/usr/bin/perl
open FILE, "$file" || die "Can't open: $! n";
print "$file open";
If "$file" doesn't exist, you won't get the "Can't open" message. The problem is that the "||" binds tightly and confuses the "open" function. You need to either do:
open FILE, "$file" or die "Can't open: $! n";
(because or binds less tightly than ||) or
open(FILE, "$file") || die "Can't open: $! n";
(because the parens contain the open function)
Generally speaking it's a very good idea for new Perl folk to use "or" rather than "||" in conditional flow tests, and to use parens for functions. So (following both rules), I'd recommend getting used to writing that like this:
open(FILE, "$file") or die "Can't open: $! n";
at least until you are very clear on what each of these does.
*Originally published at APLawrence.com
About the Author:
A.P. Lawrence provides SCO Unix and Linux consulting services http://www.pcunix.com
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