my $text = "This is a test for the word blue more things blue and then some very large text with a lot of things blue and done";
my @words = do {
    local $_ = $text;
    split;
};
my $WANT = qr/\bblue\b/i;
my @wants = grep { $words[$_] =~ $WANT } 0 .. $#words;
for (@wants) {
    my $first = ($_ - 5 < 0) ? 0 : $_ - 5;
    my $last  = ($_ + 5 > $#words) ? $#words : $_ + 5;
    print join( ' ', @words[$first .. $last]), $/;
}
__END__
a test for the word blue more things blue and then
the word blue more things blue and then some very large
with a lot of things blue and done