CODEWITHSUNDEEP
perlreturnsubroutine
MeirG
MeirG

Reputation: 343

Making a tidy (perl) return

It is most probably a stupid question, but here goes:

In many modules I have multiple points at which I return to the calling script. But before actually returning, I need to do some tidy-up chores, such as changing directory to the parent dir, etc.

I wrote a sub that does that for all return points. However, the only way I could think of to use it was to have

tidy_up();
return (LIST);

I would like to have a sub that accepts the returning value(s) LIST and have that sub also return to the calling script:

tidy_up_and_return(LIST);

Is that at all possible?

Upvotes: 0

Views: 52

Answers (1)

Sobrique
Sobrique

Reputation: 53478

This probably isn't a good idea. There's a bunch of subtle gotchas waiting to happen around caller context.

However - return isn't actually required by a sub - if there is no return the sub implicitly returns the result of the last calculation. 

#!/usr/bin/env perl

use strict;
use warnings;

sub parent { 
   my @results = ( "one", "two" ); 
   child ( @results, "some_other_value" ); 
}

sub child {
   return ( @_ ); 
}

print parent();

Because child returns it's parameters - as the last line of parent is to call child - then parent implicitly returns the result of child.

I would suggest that you not do this though, as I'd call it bad style - a future maintenance programmer won't necessarily know that's what you're doing.

You can maybe improve that slightly by:

return child ( @results, "some_other_value" );

But bear in mind that you can end up with some slight oddness with return context - e.g.:

#!/usr/bin/env perl

use strict;
use warnings;

sub parent {
    my @results = ( "one", "two" );
    return child( @results, "some_other_value" );
}

sub child {
    return (@_);
}

my $result =  parent();
print $result;

vs.

sub parent2 {
    my @results = ( "one", "two" );
    return ( @results, "some_other_value" );
}

my $result =  parent2();
print $result;

Looks pretty similar, but doesn't have the same result, because of the context of the operations.

Upvotes: 2

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