echo "$XXX" | perl -pe '$_=(split "/", (split ";")[0])[-1]'

##</code><code>##

my $url = "/bla/bla/123;yarg";
my @tmp = split ";", $url;    # break string at semicolons
@tmp = split "/", $tmp[0];    # break first chunk apart at "/"
print $tmp[-1];               # Print the value we want

##</code><code>##

my $url = "/bla/bla/123;yarg";

# Split on ";", keep only the first chunk, then split on "/"
my @tmp = split "/", (split ";", $url)[0];

# The last item holds the value we want
print $tmp[-1];

##</code><code>##

my $url = "/bla/bla/123;yarg";

$url = (split "/", (split ";", $url)[0])[-1];

print $url;

##</code><code>##

perl -e '$a="/bla/bla/123;yarg"; print (split "/", (split ";", $a)[0])[-1]'
print (...)_ interpreted as function at -e line 1.
syntax error at -e line 1, near ")["
execution of -e aborted due to compilation errors.

##</code><code>##

perl -e '$a="/bla/bla/123;yarg"; print +(split "/", (split ";", $a)[0])[-1]'
123