output for formula

[oysters2000]

Hi expert
I will be writing my exam next week and need some explaining on the following:

1. I need help with the following code, if possible. could you please explain how they work out the 2nd print of the string, and what does $1 stand for. I have the answer but just checking if there are other solutions.
$str ="A fox in a box trading socks";
$str =~m/..(...)../;
print ("$1 ");
$str =~m/\s+$1.in\sa\s[a-d]{1}(\w{2}); # this part i don’t understand(how do they get “ox”)
print "$1 ";
$str =~m/([stock]{6});
print "$1 ";

2. in the pre-assements of the hash’s, the second question I don’t understand how they get their answer of 52?
%hash = (1=>2
2 =>3
3 =>4);

$hash{2} = 5;
$hash = 6;
%hash = reverse(%hash);

for ($i = 1; $i < 5; $i++)
{
delete($hash{$1});
}
print(%hash)


If you could get back to I would appreciate it.

Regards mark

 

[ishnid]

$str =~m/\s+$1.in\sa\s[a-d]{1}(\w{2})/;

That regexp is matching against the original string in $str. The $1 variable currently contains 'fox' (from the first regexp). Here it is broken down:
\s+ (one or more spaces, which matches the space after 'A')
$1 (matches 'fox')
. (any character - matches the space after 'fox')
in\s (matches 'in', followed by the space aftewards)
a\s (matches 'a', followed by the space afterwards)
[a-d]{1} (one character that is a,b,c or d - matches the 'b' in 'box')
(\w{2}) (exactly 2 'word characters' (i.e. a-z, 0-9 or _) - matches the 'ox' in 'box')

Because the \w{2} is in parenthesis, whatever it matches ('ox') is stored in $1.


Second one explained:

# set up the initial hash - easy!
%hash = (1=>2,
2 =>3,
3 =>4);

# set the value of key '2' to 5.
# %hash is now 1=>2, 2=>5, 3=>4
$hash{2} = 5;

# this is a scalar unrelated to %hash
$hash = 6;

# reverse the hash - it's now 4=>3, 5=>2, 2=>1
%hash = reverse(%hash);

# delete any elements which have a key of 1, 2, 3 or 4
# hash is now 5=>2
for ($i = 1; $i < 5; $i++)
{
delete($hash{$i}); # assuming '1' should have been 'i'
}

# print 52 (<key><value>)
print(%hash);

 

[oysters2000]

I don’t understand how they get their answer as the code is not that clear.
Could some one could explain line by line how they get their answer, I would really appreciate it.




sub returnValues {
my($target, @values) = @_;
my(@results);
foreach(@values) {
$_ > $target ? push(@results, “$_\n”) : “”;
}
return @results;
}

using this subroutine, what is the output of the following perl statements?

@myNumList = (33, 35, 67, 11, 78, 99, 23, 55);
print returnValues(50, @myNumList);

 

[ishnid]

oysters2000, Please don't double-post the same question in different threads.