use happens at compile time (and calls the package's import method, if any) and require doesn't happen until run time.

"use"ing a module will tell you at compile time if you have any compilation problems, but you won't find out with require until you actually hit the "require" statement while the code is running. use is more or less equivalent to the following:

BEGIN
{
    require Foo::Bar;
    Foo::Bar->import;
}
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Typically, you want to use modules and not require them, but if you have a module that you don't want to load unless needed (perhaps in an error routine), then require it:

sub error_handling
{
    my $data = shift;
    require Data::Dumper;
    die Data::Dumper::Dumper $data;
}

# or 

sub error_handling
{
    my $data = shift;
    require Data::Dumper;
    Data::Dumper->import;
    die Dumper $data;
}
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Cheers,
Ovid

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