sub begin_work {
    use Data::Dumper;

    ... lotsa code

    no Data::Dumper;
    return;
}

##</code><code>##

Win8 Strawberry 5.8.9.5 (32)  Sun 01/10/2021 10:52:26
C:\@Work\Perl\monks
>perl -Mstrict -Mwarnings
# pm#11126693

foo();  # try disabling this statement

print Dumper [ qw(1 2 3) ];  # print() on unopened filehandle Dumper

# foo();  # try enabling this statement

sub foo {
    use Data::Dumper;
    print Dumper [ qw(a b c) ];

    no Data::Dumper;  # has no effect
    print Dumper [ qw(x y z) ];
    }

print Dumper [ qw(9 8 7) ];  # prints as expected
^Z
$VAR1 = [
          'a',
          'b',
          'c'
        ];
$VAR1 = [
          'x',
          'y',
          'z'
        ];
print() on unopened filehandle Dumper at - line 5.
$VAR1 = [
          '9',
          '8',
          '7'
        ];

##</code><code>##

sub Dumper;

print Dumper [ qw(1 2 3) ];  # print() on unopened filehandle Dumper

##</code><code>##

### sub Dumper;

print Dumper([ qw(1 2 3) ]);  # print() on unopened filehandle Dumper