uninitialized value in substitution iterator

[Aberrant]

What I'm trying to do is take %%variable%% in a file and replace it
with data returned by the subroutine substitute(). The code I have
looks like this:

$data =~ s/%%([^%]*)%%/&substitute($1)/ge;

And it does exactly what I want, but it also fills up my error log
with this:

"Use of uninitialized value in substitution iterator"

Can someone shed some light on this? How can I get around the warning?
Or rather, why is it being generated and how can I do what I want and
make perl happy? Thanks,

Abe

 

[Gunnar Hjalmarsson]

What I'm trying to do is take %%variable%% in a file and replace it
with data returned by the subroutine substitute(). The code I have
looks like this:

$data =~ s/%%([^%]*)%%/&substitute($1)/ge; -------------------------^
redundant

And it does exactly what I want, but it also fills up my error log
with this:

"Use of uninitialized value in substitution iterator"

Can someone shed some light on this?

The file probably includes variables that are unknown by the
substitute() function. You can for instance do something like this:

sub substitute {
my $key = shift;
my %vars = (
var1 => 'aaa',
var2 => 'bbb',
...
);

if ( $vars{$key} ) {
$vars{$key};
} else {
warn "Unknown template variable: $key";
"%%$key%%";
}
}

 

[public]

$data =~ s/%%([^%]*)%%/&substitute($1)/ge;

-------------------------^
redundant

What's redundant, the ampersand? Depending on how the text is displayed
the caret is pointing to parentheses.

The file probably includes variables that are unknown by the
substitute() function. You can for instance do something like this:

Thanks, that was the problem! I had this:

sub substitute
{
my $var = shift;
if (exists($subs->{$var}) && $subs->{$var} eq "readPage") {
return readPage($var);
} elsif (ref($subs->{$var}) eq "CODE") {
return &{$subs->{$var}};
} else {
return $subs->{$var};
}
}

and I changed it to this (last few lines changed):

sub substitute
{
my $var = shift;
if (exists($subs->{$var}) && $subs->{$var} eq "readPage") {
return readPage($var);
} elsif (ref($subs->{$var}) eq "CODE") {
return &{$subs->{$var}};
} elsif (exists($subs->{$var})) {
return $subs->{$var};
} else {
return "";
}
}


No more warnings, I never realized I was returning undef to s/// like
that.

 

[Gunnar Hjalmarsson]

$data =~ s/%%([^%]*)%%/&substitute($1)/ge;

------------------------^
redundant

What's redundant, the ampersand?

Yes, provided that you are using Perl 5. (It does have special meanings,
see "perldoc perlsub".)