You have introduced the array @t which is interpolated. So you have to quote the @ (or write q{h@t}).

    perl -e 'if ("h\@t" =~ /(\@)/ ) { print $1 }'
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Example for an array interpolation:

    #!/usr/bin/perl
    use strict;
    use warnings;

    my @friends = ('Margaret', 'Richard', 'Carolyn', 
                   'Rohan', 'Cathy', 'Yukiko');
    print "Friends: @friends\n";
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