The mget method does what you want:

$sftp->mget("/etc/abcd*.txt", $local_dir);
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update: Oops, that would download the files. Use glob if you just want to list them:

my $files = $sftp->glob("/etc/abcd*.txt");
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or maybe...

my $files = $sftp->glob("/etc/abcd*.txt", names_only => 1);
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