Given a limited set of delimiters, this might work.

my @delim = (",", ";", ":", "\t");
my $line = "This;is;delimited;with;a;semicolon,;and;there;is;a;comma";

for ( @delim )
{
    print "possibly delimited with $_\n"
        if $line =~ /([^$_]+$_){2,}/;
        
}
# prints "possibly delimited with ;"
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This does not handle quoted fields. But in my exp. quoted CSV-files are seldom used, so I'll leave it as it is.