create two global regexps :

• paramtest1, ^param, result is true
• paramtest2, [^#]param, result is true

create a text item and two triggers against it :
t1 - host:item.regexp(@paramtest1)
t2 - host:item.regexp(@paramtest2)

test global regexps in the frontend with 2 lines of data :

line
param

notice how paramtest1 does not match but paramtest2 matches.
now send same two lines to the item.
notice how first trigger matches but the second does not - this is the opposite what the testing in the frontend indicated