if ($line =~ m/\xDB/) {
  # $line contains character 219 (0xDB in hex)
}
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ascii code (219)

As pointed out, that's beyond ascii so it's possibly unicode. While it is certainly \xDB in hex, I'd interpret it as "FULL BLOCK" (aka "graphblock middle"). This is █ as an entity and is displayed as █ (looks like a filled block to me).

Of course, this certainly isn't standards compliant but might be what you're looking for.

I only know its ascii code (219)

<nitpick> This is not ASCII, strictly speaking... (which is 7-bit, and thus only defines codes in the range 0-127) </nitpick>

Caveat: The answers already given to you assume you don't decode the bytes you read in (using :encoding(...), decode, use open or some other means) into a string of characters. If so, you'll need to decode chr(219) and compare against that.

perl -e'die unpack q=H*=, chr 219'
db at -e line 1.

perl -e'die 1 if chr(219) =~ /\xDB/'
1 at -e line 1.
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perldoc -f chr
perldoc -f index
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