Just enclose your map in square brackets to create an array reference.

my $files_to_send = [map {"$stage/$_.pdf"} @{$self->_getGood()}];
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Look at the following example:

my @ary = qw/a b c d/;
my $var = @ary;     # $var is 4; @ary is interpreted in scalar context
my $var1 = [@ary];  #$var is ['a','b','c','d']
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