Use indentation to remove ugliness:

{
    my $bar;
    if ($foo) {
        $bar = "true";
    }
    print $bar;
}
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I suppose you could hide $bar in a subroutine:

sub test
{
    my $arg = shift;
    my $bar;
    if($arg) {
        $bar = "true";
    }
    return $bar;
}

my $foo = 1;
print test($foo);
[download]

But that's an extreme solution.

Update:
This approach eliminates the global and the curlies:

use strict;

my $foo = 1;

if ($foo) {
   package Strange;
   our $bar = "true";
}
print $Strange::bar || "false";
[download]

:-)